The Holcroft valve gear was a type of conjugated valve gear designed and patented by Harold Holcroft and used on three-cylinder steam locomotives of the South Eastern & Chatham Railway (SECR). It bore many similarities to the Gresley conjugated valve gear, which it predated, as eventually used on all Gresley's three cylinder designs. It varied from the Gresley method of operation by using the combination lever assembly instead of the valve spindles to drive the middle cylinder of a three-cylinder design. This had operational advantages over Gresley's design, namely eliminating the problems of flexure, bush wear and the influence of heat in the valve spindles.